Polyester resin composition with a long shelf life

ABSTRACT

UNCURED, CURABLE, UNSATURATED POLYESTER RESIN COMPOSITIONS CONSISTING ESSENTIALLY OF AN UNSATURATED POLYESTER, AN ETHYLENICALLY UNSATURATED MONOMER SUCH AS STYREME OR A SIMILAR MONOMER, AND ABOUT 0.1-1.5 MOLE PERCENT OF AN INHIBITOR SELECTED FROM A GROUP CONSISTING OF TETRACH&#39;&#39;OROCATECHOL, TETRACHIOROHYDROQUINONE, TETRABROMOCATECHOL, AND TETRABROMOOHYDROQUINONE HAVE SHELF LIVES IN EXCESS OF ABOUT 100 DAYS OF ABOUT 70*C.

United States Patent U.S. C]. 260-866 Claims ABSTRACT OF THE DISCLOSUREUncured, curable, unsaturated polyester resin compositions consistingessentially of an unsaturated polyester, an ethylenically unsaturatedmonomer such as styrene or a similar monomer, and about 0.1-1.5 molepercent of an inhibitor selected from a group consisting oftetrachlorocatechol, tetrachlorohydroquinone, tetrabromocatechol, andtetrabromohydroquinone have shelf lives in excess of about 100 davs atabout 70 C.

CROSS REFERENCE TO RELATED APPLICATION This is a continuation-in-part ofour copending application Ser. No. 782,735, filed Dec. 10, 1968, and nowabandoned.

BACKGROUND OF THE INVENTION The invention described and claimed hereinwas made in the course of or under a contract or subcontract thereunderwith the Department of the Air Force, Department of Defense.

This invention is in the field of stabilized, uncured polyester resincompositions which are liquids at room temperature (e.g., ca. -35" C.).More particularly, this invention is in the field of stabilized,uncured, curable, burn resistant, unsaturated polyester resincompositions, said compositions comprising about 10-45% (or about 40%)by weight of monomeric styrene (or similar ethylenically unsaturatedmonomer), about 0.25-6.4% by weight percent (ca. 0.1-1.5 mole percent,as hereinafter defined) of an inhibitor selected from a group consistingof tetrachlorcatechol, tetrachlorohydroquinone, tetrabromocatechol, andtetrabromohydroquinone, and enough uncured, unsaturated polyester tototal 100%, said compositions being a liquid at room temperature andhaving a shelf life (gel time) in excess of about 100 days at about 70C. and in excess of about 25,000 days at about C.

Although an extended shelf life at elevated temperature (e.g., a geltime in excess of about 20-30 days at 70 C.) is generally unnecessary inthe uncured, curable, burn resistant, unsaturated polyester resincompositions used commercially in North America and Europe, the extendedshelf life of the polyester resin compositions of this invention isespecially valuable in relatively undeveloped tropical and desert areassince polyester resin compositions shipped to'suchar'eas can be storedfor several weeks on open docks, in fields, or in sheds "(which lack aircon- 3,657,387 Patented Apr. 18, 1972 ice ditioning facilities) underconditions such that the temperature may reach about 50-65 C. Thecompositions of this invention are especially useful for constructingquickcuring pads for use as runways for light aircraft and forconstructing quick curing slabs to support houses, office buildings,storage sheds, and the like in primitive areas.

US. Pat. 2,779,701 (Robitschek et al., 154/43) teaches (lines 49-51 ofcolumn 14) that polymerization inhibitors (stabilizers) usuallyconstitute about 0.0011% by weight of flame-retardant polyestercompositions. US. Pat. 3,288,735 (Watanabe et al., 260/ 17.4) presents alist of inhibitors including hydroquinone, trinitrophenol,4-ethylcatechol, 3-phenylcatechol, and 3-isobutylcatechol which havebeen used to increase the gel time (shelf life) of unsaturated polyesterresin compositions.

Stabilized, uncured, curable, burn resistant, unsaturated, liquid (atroom temperature) polyester composition comprising about 10-45% byweight of monomeric styrene (or similar ethylenically unsaturatedmonomer) and about 0.0011% by weight of inhibitor and enough uncured,curable, unsaturated polyester to total 100%, are well known in the art.However, the prior art compositions differ from the compositions of thisinvention in; (a) the nature (chemical identity) of stabilizer(inhibitor or gel retarder) present; and (b) shelf life (gel time)thegel time of the prior art resins being about 15-50 days (or in someinstances less) at about C.

SUMMARY OF THE INVENTION In summary, this invention is directed to astabilized, uncured, curable, burn resistant, unsaturated polyesterresin composition consisting essentially of:

(a) An unsaturated polyester of; (i) a polyhydric alcohol selected froma first group consisting of ethylene glycol, diethylene glycol,propylene glycol, and a polyethylene glycol having a molecular Weightbetween 300 and 4000; (ii) a member selected from a second groupconsisting of chlorendic acid and chlorendic anhydride; (iii) a memberselected from a third group consisting of maleic acid, fumaric acid,itaconic acid, and aconitic acid or an anhydride of the third groupmember; and (iv) a member selected from a fourth group consisting oftricarballyic acid, citric acid, succinic acid, adipic acid, sebacicacid, azelaic acid, phthalic acid, and terephthalic acid or an anhydrideof the fourth group member, the chlorine content of the stabilizedpolyester resin composition being 20 to 30%, the mole ratio of the thirdgroup member to the fourth group member being 1:0.25-12;

(b) An ethylenically unsaturated monomer selected from a fifth groupconsisting of styrene, vinyl toluene, amethylstyrene, dimethylstyrene,the methyl a methylstyrenes, a-bromostyrene, ,B-bromostyrene,a-ChlOl'OStY- rene, B-chlorostyrene, diallylphthalate, vinyl acetate,methyl methacrylate, and divinylbenzene, the fifth group memberconstituting about 10-45% (preferably about 20-40%) of the stabilized,uncured, curable, burn resistant, unsaturated polyester resincomposition; and

(c) An inhibitor selected from a sixth group consisting oftetrabromocatechol, tetrachlorocatechol', tetrabromo- V hydroquinone,and tetrachlorohydroquinone, the sixth group member being present in anamount between about 0.1 and about 1.5 mole percent based on thestabilized, uncured, curable, burn resistant, unsaturated polyesterresin composition, said composition having a gel time of at least about100 days at 70 C.

DESCRIPTION OF PREFERRED EMBODIMENTS In a preferred embodiment(Embodiment A) of the composition described in the above summary thesecond group member is tetrabromophthalic acid or tetrabromophthalicanhydride (rather than chlorendic acid or chlorendic anhydride) and thecomposition has a bromine content of about -12% (rather than a chlorinecontent of about 2030%).

In other preferred embodiments of the compositions of; (a) the aboveSummary; or (b) Embodiment A, supra:

1) The sixth group member is present in an amount between about 0.25 andabout 1 mole percent based on the stabilized, uncured, curable, burnresistant, unsaturated polyester resin composition;

(2) About 0.030.5 mole percent of cobalt, calculated as Co, is presentin the stabilized, uncured, curable, burn resistant, unsaturatedpolyester resin composition, the cobalt being added as a soluble cobaltsalt or as an adduct of such cobalt salt and a member selected from thesixth group, the mole ratio of cobaltzsixth group member in said adductbeing about 1:1;

(3) A member selected from a seventh group con sisting of tertiarybutylcatechol and methylhydroquinone is present, the seventh groupmember being present in an amount between about 0.1 and about 1 molepercent based on the stabilized, uncured, curable, burn resistant,unsaturated polyester resin composition; and

(4) The fifth group member is styrene.

DETAILED DESCRIPTION OF THE INVENTION It is an object of this inventionto provide a stabilized, uncured, curable, burn resistant, unsaturatedpolyester resin composition having a shelf life of at least about 100days at about 70 C. It is another object to provide several new andnovel inhibitors excellently adapted for accomplishing the aforesaidobject. Other objects of the invention will be readily apparent to thoseskilled in the art.

The aforesaid objects have been accomplished by incorporating suchquantity of at least one additive selected from a group consisting oftetrachlorocatechol, tetrachlorohydroquinone, tetrabromocatechol, andtetrabromohydroquinone into an uncured, curable, burn resistant,unsaturated polyester resin composition that the inhibitor content ofthe resulting stabilized polyester resin composition will fall within arange of about 0.1-1.5 (or 0.25-1 or 0.5-0.8) mole percent.

In general, unsaturated polyester resins are prepared by theesterification of alphabeta-unsaturated polybasic acids, and dihydricalcohols. Certain compounds of this type can be indicated generically asfollows;

where, M- represents an unsaturated dibasic acid moiety and G representsa dihydric alcohol moiety. Modifying dibasic acids may also be used inthe polyester resin compositions. Representative dihydric alcohol andunsaturated polybasic acids are shown below.

In preparing unsaturated polyesters which can be employed in thepractice of the present invention, the alcohol component may compriseethylene glycol, diethylene glycol or propylene glycol, or one of thegroup of solid polyethylene glycols designated as Carbowax.

Polyethylene glycols such as the Carbowaxes are understood to havemolecular weights above 300. Those most useful for this invention haveweights below 4000 and preferably are in a range of about 1000 to 2000,e.g., 1500.

The acid component usually comprises an alphabetaethylenicallyunsaturated polycarboxylic acid such as maleic, fumaric or itaconicacid, or the well-known derivatives of these polycarboxylic acids havingethylenic unsaturatation in alpha beta-relation to a carboxyl group.Polybasic acids such as aconitic acid, tricarballylic acid or citricacid may also be employed. A plurality of such acids also may be mixedwith each other, if so desired. In many instances, it may be desirableto include a dicarboxylic acid free of ethylenic unsaturation. Examplesof this latter type of dicarboxylic acid include phthalic acid orterephthalic acid, which, although they contain double bonds in thebenzene ring, do not undergo addition reaction with monomer compoundsand may, therefore, be considered as being the equivalent of saturatedcompounds. Likewise, aliphatic dicarboxylic acids such as succinic acid,adipic acid, sebacic acid, or azelaic acid may be substituted for a partof the alphabeta-ethylenically unsaturated dicarboxylic acid. Theproportion of the non-ethylene acid with respect to thealphabeta-ethylenically unsaturated acid is susceptible of widevariation. Halogen-containing (generally saturated) acids are includedto render the cured polymers made by copolymerizing the polyester withstyrene (or the like) burn resistant. These halogen-containing acids aregenerally added in such quantity that the uncured polyester compositionsformed by admixing the polyester with styrene (or a similarethylenically unsaturated monomer) contain about 512% bromine or about20-30% chlorine. A molecular proportion of 0.25 to 12 moles of saturatedacid per mole of unsaturated acid is usually used for commercialapplications. Also, acid anhydrides of these dicarboxylic acids can beused instead of the dicarboxylic acids.

In preparing the polyester, a small excess (e.g., ca. 5-10%) of thedihydric alcohol is sometimes employed. The conditions of theesterification reaction are those conventionally employed in preparingpolyesters. For example, the mixture of the alcohol and the acid isheated in a vented container or under an inert atmosphere until thewater of reaction is expelled from the system, which usually occurs in atemperature range of about to 210 C. The reaction is continued until theacid value is reduced to a reasonable low point, e.g., within a range ofabout 5 to 50, or until the mixture becomes highly viscous or even solidwhen it is cooled. Usually, these conditions are attained in a period of2 to 20 hours. In any event, the reaction is concluded before theproduct becomes infusible and insoluble because of the advanced stage ofpolymerization. The product is then blended with the ethylenicallyunsaturated monomer in such a manner as to maintain the temperature ofthe blend below about 65 C.

The preferred ethylenically unsaturated monomers for use in preparingthe compositions of this invention are liquid compounds in which thepolyester component is soluble. These monomers contain the C=CH group--preferably with said group attached to a negative radical such as abenzene ring, a chlorine atom, an ester linkage, a nitrile group, or thelike. These ethylenically unsaturated monomers are free of carbon-carbonconjugated double bonds. While many monomers which can be used in thecomposition of our invention will be readily apparent to those skilledin the art, we prefer to use a members selected from a group consistingof styrene, vinyl toluene, a-methylstyrene, dimethylstyrene, themethyl-a-methylstyrenes, a-bromostyrene, ,B-bromostyrene,a-chlorostyrene, fi-chlorostyrene, diallylphthalate, vinyl acetate,methyl methacrylate, and divinylbenzene.

In general, the ratio of ethylenically usaturated monomer component (orcomponents where using at least two such monomers) to the polyestercomponent can vary over a relatively broad range, but, usually, theamount of such monomer is less (on a weight basis) than the amount ofthe polyester component. Usually, the percentage of said monomer willfall within a range of about 10 to 45 precent by weight of the totalmixture of polyester and monomer, and the preferred range of saidmonomer is, in most instances, about 20 to 40 percent.

The polyester resin compositions of this invention contain about 20-3chlorine or about 12% bromine and are burn resistant i.e., upon curing(crosslinking between the polyester component and the ethylenicallyunsaturated monomer (e.g., styrene) component of the composition theyform copolymers which are very resistant to burning because of theirsubstantial halogen content). The polyesters used in preparing thepolyester compositions of this invention are prepared by esterifyingmixtures of dibasic acids and/or anhydrides with a difunctional glycol.Part of the acid moieties are unsaturated, and the final polyester isdiluted with styrene or the like. The resin for end-use applications iscured with a peroxide catalyst in the presence of a cobalt or similar(e.g., vanadium, iron, or the like) promoter to develop the finalcrosslinked three dimensional thermoset copolymer product.

The curing time of the polyester resin systems varies between about 1minute and about 24 hours. This time span depends, in part, upon suchvariables as type of polyester resin, amount of catalyst, and amount ofinhibitor. The curing temperature of the polyester resin systems variesbetween about 15 C. and about 250 C. Preferably, the polyester resinsystems are cured at room temperature (15 to 35 Q).

As the scope of useful polyester resin systems is extensive, the type ofpromoter which can be used in those systems is also extensive. A fewexemplary promoters are given in the following paragraphs.

One of the promoter types which can be used in the polyester resinsystems is a cobalt salt which is capable of being dissolved in theresinous composition. US. Pat. No. 3,288,735, teaches the use of cobaltsalts, e.g., cobalt naphthenate, to decrease the gelation time ofpolyester resin compositions comprising a polyester resin havingalphabeta-unsaturation, a monomer having an unsaturated bond, andcertain inhibitors. Other cobalt salts excellently adapted for use inpromoters in the compositions of this invention are cobalt octoate orany other higher fatty acid salt of cobalt. The amount of cobalt saltcan be varied from about 0.001 to 0.3 percent of the salt calculated asdissolved metallic cobalt based on the total weight of the composition.On the same basis, the preferred amount of cobalt metal generally rangesfrom about 0.05 to 0.15 percent.

, Vanadium promoters disclosed in U.S. Pat. No. 3,333,- 021 are useful.Other promoters, including iron, are well known to those skilled in theart.

The promoter can be admixed with the polyester composition before thecomposition is placed in storage or it (the promoter) can be admixedwith the composition at any time before curing the composition.

The polyester resin systems of this invention can also contain othercompatible additives, such as fillers (silica, talc, mica, clay, carbonblack, etc.), dyes, reinforcing materials (asbestos, chopped glassfibers), etc.

The resin systems stabilized with agents of this invention are readilycurable, for example, when excess peroxide catalysts and cobalt promoterare employed to destroy, neutralize, or inactivate the inhibitors. Thepreferred catalysts are disclosed in copending application Ser. No.782,734 (Disclosure No. 2693); filed Dec. 10, 1968; D. A. Daniels, R. L.Orem, and E. W. Lard, Applicants. For example, the preferred catalystsfor curing the resin systems include a ketone peroxide, such as Lupersol224, Lupersol DDM, methylethyl ketone peroxides, and the like, and anorganic nonketonic diperoxide, such as Lupersol 256. The amount of eachpreferred catalyst component must be based on the amount of eachstabilizer present. In general, the non-ketonic diperoxide can bepresent in an amount between about 2 to about 3 percent by weight basedupon the resin composition (polyester plus monomers, etc.) present andthe ketone peroxide can be present in an amount between about 2 to about6 percent by weight based upon the amount of resin components. Theamount of cobalt promoter present is preferably between about 0.2 toabout 0.4 mole percent based on the resin composition.

The instant invention will be better understood by referring to thefollowing specific but nonlimiting examples. It is understood that saidinvention is not limited by these examples which are offered merely asillustrations; it is also understood that modifications can be madewithout departing from the spirit and scope of the invention.

EXAMPLES.PREPARATION OF RESINS Example 1 Polyester composition A wasprepared by admixing and heating (as hereinbefore described) 10 moles ofdiethylene glycol, 4 moles of maleic anhydride, 5 moles of chlorendicanhydride, 1 mole of adipic acid, 10 moles of styrene, and about 0.02mole of cobalt octoate. There was a total halogen content of about 25percent.

Example 2 Polyester composition B was prepared by admixing and heating(as hereinbefore described) 10 moles of diethylene glycol, 5 moles ofmaleic anhydride, 5 moles of chlorendic anhydride, and 10 moles ofstyrene. There was a total halogen content of about 25 percent. (Acobalt compound, or other catalyst, must be placed in the compositionbefore it can be cured after storage.)

Example 3 Polyester composition C was prepared by admixing and heating(as hereinbefore described) 10 moles of diethylene glycol, 5 moles ofmaleic anhydride, 5 moles of chlorendic anhydride, 10 moles of styrene,and about 0.02 mole of cobalt octoate. There was a total halogen contentof about 25 percent.

Example 4 Polyester composition D was prepared by admixing and heating(as hereinbefore described) 10 moles of diethyl glycol, 62 moles ofmaleic anhydride, 1.2 moles of tetrabromophthalic anhydride, 2.6 molesof phthalic anhydride and 10 moles of styrene. There was a total halogencontent of about 9 to about 11 percent. (A cobalt compound, or othercatalyst, must be placed in the composition before it can be cured afterstorage.)

Example 5 Polyester composition E was prepared by admixing and heating(as hereinbefore described) 10 moles of diethyl glycol, 6.2 moles ofmaleic anhydride, 1.2 moles of tetrabromophthalic anhydride, 2.6 molesof phthalic anhydride, 10 moles of styrene, and about 0.02 mole ofcobalt octoate. There was a total halogen content of about 9 to about 11percent.

DETERMINATION OF GEL TIME Example 6 We determined the gel time '(shelflife) of our polyester resin compositions (With and without the additionof inhibitors) by using the following procedure which is based upon aprocedure published by Cass and Burnett (Ind. Eng. Chem, 1954, 46,1619-1624).

A sample of polyester resin composition was placed in a test tube havinga diameter of about /2 inch and a height of about 4 inches. Sufficientsample was added to fill the tube within about an inch of its top, and acork stopper was inserted tightly into the top of the tube leaving anair column (bubble) about /2 inch in height between the top of thesample and the bottom of the stopper. The stoppered tube was immediatelyplaced in an oven at a preselected temperature and examined from time totime by inverting it (the tube) and noting whether or not the airbubbles would rise when the tube was inverted. The gel point was takenas the point at which the bubble ceased to rise when the tube was inis aconstant. Hence, when log 1/t (where t is time, in days, in whichgelation occurs) is plotted against l/T K.), a line is obtained having aslope identical with that of the line represented by a plot of l/ T K.)vs.

verted. Gel time (at the preselected temperature) was 5 log k. the time(hours or days at said temperature) required for It is convenient toplot the colog of l/ t (or log t itself) the sample to reach its gelpoint. Precision (reproducivs. l/ T K.) to obtain a line of the sameslope but of bility) between runs, as determined by making a numberopposite sign. The straight line obtained by plotting of runs induplicate or triplicate, was found to be about log t vs. l/T K.) can beextrapolated to any l/ T i5-l0%. value required within a range of about27344S K. thus Since shelf life (gel time) determination on thesta-bipermititng accelerated storage tests based on this use of lizedpolyester resin compositions of this invention would higher testtemperatures. This permits a rapid laboratory be both tedious and of animpractically long duration determination of whether or not an inhibitorprevents if made at 70 C. (because these compositions have gel setting(gelation) of a polyester resin composition prior times in excess of 100days at 70 C., the actual deterto combination with a catalyst curingsystem for an end minations were made using 125 C. as the aboveuseapplication. mentioned preselected temperature. The thus obtained Thefollowing table (Table I) shows the results of 4 gel times (gel times at125 C.) were adjusted to g l tests of gel time made with polyester resincomposition times at 70 C. by using an Arrhenius type relationship B (acontrol and 3 runs with inhibitors) at 125 C. and set forth in theequation k=Ae" which reduces to log these gel times adjusted to 70 C.

TABLE I k=C1- Gel time, polyester resin composition B Corresponding gelwhere k=rate of crosslinking of the resin at temperature Gel time at 125C., days: time at 70 C., days T K.), E=energy of activation in caL/mole,R=l.987 0.3 1 9 cal.; and C is a constant equal to log A, the frequency2 2 120 factor or collision frequency. The rates of crosslinking l0 700(i.e., gelling) of polyester resin formulations of Examples 99 2 4,500 1through 5 when plotted on semi-log paper (log k vs. 1/ T 1 control, noinhibitor present. K.)) each fall on a straight line for the temperatureInhibitor present. range This Straight line relationship estab' Thefollowing table (Table II) presents a summary of lishes the fact thatthe mechanism of the gelling reaction the results obtained in a Seriesof runs using; (a) no does not change Over the temperature range ofinterest, hibitor; (b) some conventional inhibitors; (c) the inahd theSlope of the and the aetihibitors of this invention; (d) conventionalinhibitors plus Vation energy of the gelattoh, can be calculated foreach a cobalt promoter; and (f) inhibitors of this invention plusIeSiIla cobalt promoter. These results show the superiority of isPossible to p y the extrapolation of Shelf life the inhibitors of thisinvention over conventional inhibi- Of a resin composition to atemperature other than that 40 tors. Said results also show that thepoint presence of a at Which it Was determined y using a Procedure Whiehcobalt promoter and an inhibitor of the instant invention in ypCalculation of the reaction Iate- The change in a polyester resincomposition produces a greater increase viscosity which occurs uponaging results from crosslinkin shelf life (gel time) at 70 C. than thesame inhibitor ing and conversion of the fluid polyester into anon-flowwithout the cobalt promoter although the cobalt promoter ablegel; this change is substantially constant for each without theinhibitor does not increase gel time. These particular polyesterformulation. Therefore, the rate of crosslinking expressed in terms ofrate of change of viscosity (i.e., Aviscosity/ time) becomes C /timewhere C results show that a cobalt promoter does not produce a similarbeneficial effect where used in combination with a conventionalinhibitor.

TABLE II.GEL TIME, DAYS AT 70 C.

Polyester 1 Polyester Polyester 1 Polyester Polyester 1 Additive comp. Acomp. B comp. C comp. D comp. E

None- 9 l0 0.05 mole percent cobalt octoate.-. 9 8 10 1 mole percenthydroquinone 35 1 mole percent hydroquinone 22 30 25 0.05 mole percentcobalt octoate-.. 0.5 mole percent tctratluorocatecho 35 0.05 molepercent cobalt octoate 1 mole percent 3,4,6-tribromocathechol 2 u} 300.05 mole percent cobalt octoate 1 mole percent; mcthylhydroquinone 2 421 mole percent mcthylhydroquinone 62 20 13 0.05 mole percent cobaltoctate 1 mole percent tertiary butylcatcchol 35 30 1 mole percenttertiary butylcatechol 12 11 10 0.05 mole percent cobalt octooate 1 molepercent tetrabromocatcchol 1 mole percent tctrabromocatechol 0.05 molepercent cobalt octoate 1 mole percent tetrabromocatechol 0.2 molepercent cobalt octoatc 0.5 mole percent tetrabromocatcchol 3 0.05 molepercent cobalt octoatc 0.25 mole percent tctrabromocatechol 0.25 molepercent cobalt 8 0.5 mole percent tctrabromocatechol 3 0.25 mole percentcobalt 5 See footnotes at end of table.

TABLE II.Cnziiinued Polyester Polyester Polyester 1 Polyester Polyester1 Additive comp. A comp. B comp. O comp. D comp. E

0.2 mole percent tetrabromoeatechol 3 0.8 mole percentmethylhydroquinone 10, 000 0.05 mole percent cobalt octoate 0.25 molepercent tetrabromohydroquinone 700 0.25 mole percent tertiarybutylcatechol 2 1.25 mole percent tetrachlorocatechol 0.5 mole percenttetrachlorocatechol 3 0.25 mole percent tetrachlorocateehol 0.25 molepercent cobalt B 1 mole percent tetrachlorohydroquinone B 0.25 molepercent tetrachlorohydroquinone 600 0.25 mole percent cobalt B 1 molepercent tetrachlorohydroquinone 0.05 mole percent cobalt octoate In theinstances of polyester resin compositions A, O," and E, the cobalt inthe list of additives includes the 0.05 mole percent of cobalt added ascobalt octoate Where preparing the respective resin compositions. (SeeExamples 1, 3, and 5, supra).

3 Inhibitor of the prior art.

3 Inhibitor of the instant invention.

4 Cobalt naphthenate was admixed and reacted with tetrabromocatecbol indiethyl phthalate and maintained at about 135 C. for an hour. Theresulting product was found to be an adduct of cobalt naphthenate andtetr abromocatechol, the mole ratio of cobalt:tetrabromocatechol beingabout 1:1. A mixture (50% adduct and 50% diethyl phthalate) was added tothe polyester resin composition in such quantity as to provide 0.25 molepercent tetrabromocatechol and 0.25 mole percent cobalt (as Co) based onthe Weight of the polyester resin composition.

5 After admixing sutlicient cobalt naphthenate with the polyester resincomposition to bring the total cobalt content thereof to about 0.25 molepercent, sufficient tetrabromocatechol was admixed with the resincomposition to bring the tetrabromocatechol content thereof to about 0.5mole percent.

5 Cobalt naphthenate was admixed and reacted with tetrachlorocatechol indiethyl phthalate and maintained at about 135 C. for an hour. Theresulting product was found to be an adduct of cobalt naphthenate andtetrachlorocatechol, the mole ratio of cobalt:tetrachloroeatechol beingabout 1:1. Amixture (50% adduct and 50% diethyl phthalate) was added tothe polyester resin composition in such quantity as to provide 0.25 molepercent tetraehlorocatechol and 0.25 mole percent cobalt (as 00) basedon the weight of the polyester resin composition.

1 After admixing sufificlent cobalt naphthenate with the polyester resincomposition to bring the total cobalt content thereof to about 0.25 molepercent, sufficient tetrachlorohydroquinone was admixed with the resincomposition to bring the tetrachlorohydroquinone content thereof toabout 0.25 mole percent.

8 Other runs (not included in Table II) were made with excellent resultsusing cobalt adducts prepared by reacting cobalt naphthenate or cobaltoctoate with tetrachloroeatechol, tetrabromohydroquinone,tetrabromocatechol, or tetrabromohydroquinone in xylene, or apyridylpropanol.

CURING THE STABILIZED POLYESTER Example 11 RESIN COMPOSITION Example 7 Aportion of polyester resin composition C which had been stabilized withabout 1 mole percent tetrabromocatechol was admixed with Lupersol 224and Lupersol 256 (these Lupersols are peroxide catalysts, i.e.,polymerization initiators). These materials were admixed in the Example9 was repeated, except that the solvent in the 1,2-peroxycyclopentanesolution was a 50/50 mixture of water and hexylene glycol. A well-curedresin was obtained.

' Example 12 Example 9 was repeated, except that the1,2-peroxycyclopentane was replaced with:

following proportions; (a) 93.6% stabilized (inhibited) 0 0 polyesterresin composition; (b) 3.7% Lupersol 224; and (c) 2.7% Lupersol 256-.The resulting mixture was cured I I by heating to a temperature betweenC. and 82 C. for 25 minutes. The curing reaction was exothermic andautoaccelerative. The resin system gelled after 20 minutes and the peaktemperature was about 120 C. A wellcured polyester resin was obtained.After 24 hours, the fiexural modulus was 200,000 pounds per square inch(p.s.i.).

Example 8 Example 7 was repeated, except that polyester resincomposition B was used (the inhibitor was tetrabromocatechol), and 0.02mole percent of cobalt octoate was admixed before curing. A well-curedpolyester resin was obtained with a flexural modulus of 250,000 p.s.i.after 24 hours.

Example 9 An uncured polyester resin system, containing 18.1 weightpercent fiber glass, 3.7 weight percent 3,5-dimethyl-3,S-dihydroxy-1,2-peroxycyclopentane solution parts dissolved in 70parts of propylene glycol), 2.7 weight percent Lupersol 256, and 74.0weight percent of the polyester resin composition A (which wasstabilized with 1 mole percent tetrabromocatechol), and sufiicientadditional cobalt octoate to make 100% was prepared. The aforesaidsystem was then cured by heating to about 40- 80 C. The flexural modulusof the cured material, after 24 hours was 410,000 p.s.i.

Example 10 Example 9 was repeated, except that the solvent in the1,2-peroxycyclopentane solution was hexylene glycol. A well cured resinwas obtained.

A Well-cured resin was obtained.

As used herein the term percent unless otherwise defined where used,means parts per hundred by weight.

As used herein the term mole percent (mole percent) means one mole in10,000 grams of resin composition (i.e., one centimole (0.01 mole) perhundred grams of resin composition. Thus, to prepare a resin compositioncontaining 1 mole percent of tetrabromocateohol, one would admix 1 mole(ca. 426 grams) of tetrabromocatechol with enough resin composition (ca.9,574 grams) to produce 10,000 grams of inhibited resin composition.

As used herein the term mole has its generally accepted meaning; i.e., amole of a substance is that quantity of said substance which containsthe same number of molecules of said substance as there are carbon atomsin exactly 12 grams of pure 12 C.

As used herein the term stabilized, uncured, curable, burn resistant,unsaturated polyester resin composition means an unsaturated polyesterwhich; (a) has been admixed with styrene or a similar ethylenicallyunsaturated monomer to form a composition which may or may not contain acobalt or similar accelerator; (b) has been stabilized (had its gel timeextended to at least days at 70 C.) by admixing with a suflicientquantity of at least one of the inhibitors (stabilizers) recited in theabove Summary to make the total inhibitor content of the compositionabout 0.1-1.5 mole percent; (0) has not been cured (i.e., has not beengelled, or polymerized by crosslinking with the styrene or the like)present therein; and (d) can be cured by treating with a suitableperoxide catalyst (in the presence of a cobalt or other promoter) toyield a burn resistant crosslinked copolymer with styrene (or similarethylenically unsaturated monomer present in the uncured composition).It will be obvious to those skilled in the art that the uncuredcomposition of this invention will burn where the ethylenicallyunsaturated monomer present therein is styrene or a similar inflammablesub stance. In other words, the term burn resistant as used in thisspecification means that the composition, which may be quite inflammableper se, will, upon curing, yield a burn resistant copolymer.

As used herein the term inhibitor (or stabilizer) means a substance ormixture of substances which will extend the gel time or shelf life(i.e., will retard or prevent the polymerization or crosslinking duringstorage) of the unsaturated polyester and styrene (or otherethylenically unsaturated monomer) which comprise a polyestercomposition.

As used herein the term a soluble cobalt salt means a cobalt salt whichis soluble in a polyester resin composition such as those described inExamples 1-5, supra.

As used herein the expression K. means temperature in degrees Kelvin(i.e., absolute temperature).

Lupersol DDM is a solution comprising 60% methyl ethyl ketone peroxidesand hydroperoxides in dimethyl phthalate. Lupersol 224 is a solutioncomprising 30% 3,5- dimethyl-3,5-dihydroxy-1,2-peroxycyclopentane intriethyl phosphate. Lupersol 256 is a difunctional polyester catalystdesigned especially for elevated temperature applications comprising atleast 90% 2,5-dimethyl-2,5-bis(Z-ethyl hexanoylperoxy)hexane and havingat least 6.69% available oxygen.

Burn resistant polymers or copolymers are also called fire retardantpolymers or copolymers.

We claim:

1. A stabilized uncured, curable, burn resistant, unsaturated polyesterresin composition consisting essentially of;

(a) an unsaturated polyester of; (i) a polyhydric alcohol selected froma first group consisting of ethylene glycol, diethylene glycol,propylene glycol, and a polyethylene glycol having a molecular weightbetween 300 and 4000; (ii) a member selected from a second groupconsisting of chlorendic acid and chlorendic anhydride; (iii) a memberselected from a third group consisting of maleic acid, fumaric acid,itaconic acid, and aconitic acid or an anhydride of the third groupmember; and (iv) a member selected from a fourth group consisting oftricarballyic acid, citric acid, succinic acid, adipic acid, sebacicacid, azelaic acid, phthalic acid, and terephthalic acid or an anhydrideof the fourth group member, the chlorine content of the stabilizedpolyester resin composition being 20 to 30%, the mole ratio of the thirdgroup member to the fourth group member being 1:0.25-12;

(b) an ethylenically unsaturated monomer selected from a fifth groupconsisting of styrene, vinyl toluene, ot-methylstyrene, dimethylstyrene,the methyl-amethylstyrenes, a-bromostyrene, p-bromostyrene, OL-chlorostyrene, fi-chlorostyrene, diallylphthalate, vinyl acetate, methylmethacrylate, and divinylbenzene, the fifth group member constitutingabout -45% of the stabilized, uncured, curable, burn resistant,unsaturated polyester resin composition; and

(c) an inhibitor selected from a sixth group consisting oftetrabromocatechol, tetrachlorocatechol, tetrabromohydroquinone, andtetrachlorohydroquinone, the sixth group member being present in anamount between about 0.1 and about 1.5 mole percent based on thestabilized, uncured, curable, burn resistant, unsaturated polyesterresin composition, said composition having a gel time of at least about100 days at 70 C.

2. The composition of claim 1 in which the sixth group 12 member ispresent in an amount between about 0.25 and about 1 mole percent basedon the stabilized, uncured, curable, burn resistant, unsaturatedpolyester resin composition.

3. The composition of claim 1 in which about 0.03-0.5 mole percent ofcobalt, calculated as Co, is present in the stabilized, uncured,curable, burn resistant, unsaturated polyester resin composition, thecobalt being added as a soluble cobalt salt or as an adduct of suchcobalt salt and a member selected from the sixth group, the mole ratioof cobaltzsixth group member in said adduct being about 1:1.

4. The composition of claim 1 in which a member selected from a seventhgroup consisting of tertiary butylcatechol and methylhydroquinone ispresent, the seventh group member being present in an amount betweenabout 0.1 and about 1 mole percent based on the stabilized, uncured,curable, burn resistant, unsaturated polyester resin composition.

5. The composition of claim 1 in which the fifth group member isstyrene.

6. A stabilized uncured, curable, burn resistant, unsaturated polyesterresin composition consisting essentially of;

(a) an unsaturated polyester of; (i) a polyhydric alcohol selected froma first group consisting of ethylene glycol, diethylene glycol,propylene glycol, and a polyethylene glycol having a molecular weight between 300 and 4000; (ii) a member selected from a second groupconsisting of tetrabromophthalic acid and tetrabromophthalic anhydride;(iii) a member selected from a third group consisting of maleic acid,fumaric acid, itaconic acid, and aconitic acid or an anhydride of thethird group member; and (iv) a member selected from a fourth groupconsisting of tricarballyic acid, citric acid, succinic acid, adipicacid, sebacic acid, azelaic acid, phthalic acid, and terephthalic acidor an anhydride of the fourth group member, the bromine content of saidcomposition being about 5l2%, the mole ratio of the third group memberto the fourth group member being 1:0.25- 12;

(b) an ethylenically unsaturated monomer selected from a fifth groupconsisting of styrene, vinyl toluene, amethylstyrene, dimethylstyrene,the methyl-a-methylstyrene, u-bromostyrene, ,B-bromostyrene,a-chlorostyrene, ,B-chlorostyrene, diallylphthalate, vinyl acetate,methyl methacrylate, and divinylbenzene, the fifth group memberconstituting about 10-45% of the stabilized, uncured, curable, burnresistant, unsaturated polyester resin composition; and

(c) an inhibitor selected from a sixth group consisting oftetrabromocatechol, tetrachlorocatechol, tetrabromohydroquinone, andtetrachlorohydroquinone, the sixth group member being present in anamount between about 0.1 and about 1.5 mole precent based on thestabilized, uncured, curable, burn resistant, unsaturated polyesterresin composition, said composition having a gel time of at least aboutdays at 70 C.

7. The composition of claim 6 in which the sixth group member is presentin an amount between about 0.25 and about 1 mole percent based on thestabilized, uncured, curable, burn resistant, unsaturated polyesterresin compos1tion.

8. The composition of claim 6 in which about 0.030.5 mole percent ofcobalt, calculated as Co, is present in the stabilized, uncured,curable, burn resistant, unsaturated polyester resin composition, thecobalt being added as a soluble cobalt salt or as an adduct of suchcobalt salt and a member selected from the sixth group, the mole ratioof cobalt:sixth group member in said adduct being about 1:1.

9. The composition of claim 6 in which a member selected from a seventhgroup consisting of teriary butylcomposition.

10. The composition of claim 6 in which the fifth group member isstyrene.

References Cited UNITED STATES PATENTS Anderson 260-864 Robitschek eta1. 260-864 Cyba 26045.75 Watanabe et a1 260-114 14 3,341,492 9/1967Champ et a1 260-4595 3,377,407 4/1968 Kressin et a1. 260863 OTHERREFERENCES 5 Bjocksten; Polyesters and Their Applications; (1956) pp. 52and 53.

Mieziva; The Effect of Inhibitor Structure on Unsaturated PolyesterResins, Kunststofie 56(a) 1966, pp. 619- 625.

WILLIAM H. SHORT, Primary Examiner R. J. KOCH, Assistant Examiner US.Cl. X.R.

Eimers et a1 15 26023 P, 40 R, 45.8, 45.9, 45.95, 863, 864, 869

